In power systems with a high proportion of renewable energy generation (REGs) connected to the power grid, the problem of system inertia shortage, which significantly threatens the frequency stability of the system, is becoming increasingly serious. However, the previous unit commitment (UC) optimized dispatching model only focuses on the frequency regulation of the power source, whereas the frequency regulation ability of the load side is not considered. To fill this gap, this study constructs a bi-level optimized dispatching model applied to power systems with high proportion of REGs penetration. The inner layer synthetically considers the frequency response capabilities of the power-source REGs, synchronous generators, and load-side induction motors. This layer aims to solve the virtual inertia and frequency regulation capacity requirements of the REGs under the premise of frequency security. Based on the UC, the outer layer quantifies the frequency regulation cost of REGs to achieve optimal UC decisions under the prerequisite of ensuring frequency security. Taking the IEEE 39-bus power system as the original model, this study provides empirical evidence that the proposed bi-level optimization model can reduce the operating cost of the system to a certain extent and satisfy the demand for inertia and frequency regulation capacity under the precondition of security.